RU2319918C2 - Multi-pass shell-and-tube heat-exchanger - Google Patents

Abstract

FIELD: chemical, petrochemical, power and other industries, particularly heat-exchanging equipment.

SUBSTANCE: heat-exchanger comprises tube plates with tubes secured thereto and arranged in cylindrical shell. The cylindrical shell has lids, which defines end solution tanks along with tube plate bottoms. The solution tanks are separated into inlet, outlet and bent sections with partitions. The sections communicate direct and reverse heat-exchanging tubes to create single solution circulation path. Bent sections have partitions installed on tube plates between direct and reverse tubes to create cavities communicated with each other through bypass orifices formed under lids. Cavities located over solution inlet tubes of each of direct and reverse tube have honeycomb/cellular grids with direct guiding plates providing flow stabilization. The guiding plates are mounted so that they are flush with upper partition edges.

EFFECT: decreased hydraulic friction.

4 cl, 3 dwg

Description

The invention relates to heat exchange equipment and can be used in chemical, petrochemical, energy and other industries where heating or cooling of process liquids and solutions is carried out.

Shell-and-tube multi-pass heat exchangers are among the most commonly used surface heat exchangers in which heat transfer between heat-exchanging media occurs through a heat-exchange surface separating them.

Known shell-and-tube multi-pass vertical heat exchanger containing a cylindrical body with covers, in which are installed tube sheets with heat-exchange tubes fixed to them (Kasatkin A.G., "Basic processes and apparatuses of chemical technology". - M.: Chemistry, 1973, p.z27, Fig. VIII-II /). Housing covers and tube sheets with tubes form end mortar chambers that divide the body cavity into the tube and annular spaces. A feature of the device is that longitudinal partitions are installed in the caps of the mortar chambers so that the mortar chambers with nozzles for supplying and discharging the process fluid are divided into inlet / first stroke, outlet and rotary cavities. In this case, the partitions divide the tube bundle into sections or passages, which reduces the total cross section of the tubes in each section with increasing fluid velocity in the tube space and, accordingly, the heat transfer intensity (the device is taken as a prototype).

The disadvantages of the known heat exchanger are that when the processed fluid moves in the rotary chambers due to centrifugal forces arising from the rotation with a change in the direction of fluid movement by 180 °, its main / transit flow is squeezed to the wall that is as far away from the tube sheet as possible. The explanatory figure 1 shows that after the rotation and movement of the fluid to the tube sheet, the uneven velocity in the flow is maintained and, moving along the wall and running onto the tube sheet, the fluid flow fills only part of the inlet ends of the tubes. In the tubes of the central part of each section, the movement of the liquid is weakly expressed and is determined only by the ejective effect of its flow through other heat exchange tubes. Heat exchange tubes with this fluid movement practically do not participate in the heat transfer process and are the reason for the operation of the heat exchanger with reduced efficiency compared to the possible one. In addition, in the rotary chamber between the fluid flow exiting the heat exchange tubes of the forward-flow tube bundle and the flow entering the heat-exchange tubes of the reverse flow tube bundle, a vortex zone arises, intensively rotating, mixing and deforming not only the outgoing, but also the incoming flows, and thereby creating substantial hydraulic resistance. This vortex zone also increases due to the suction action of the solution flows from the inlet ends of the tubes, as a result of which an additional parasitic stream is formed. The negative consequences from the leakage of a deformed / incomplete cross-section / flow onto the tube sheet in the rotary chamber are similar to the consequences of uneven distribution of the working fluid through the tube sheet entering the heat exchanger through a narrowed inlet pipe.

Thus, these disadvantages cause a reduced thermal efficiency of the device as a whole.

These shortcomings stimulated the search for new technical solutions.

The proposed device is aimed at solving the problem of reducing the hydraulic resistance of the solution channel by uniformly distributing the rotary flow along the front of the pipe channels formed by the tube bundles.

The technical result is achieved by the fact that in a heat-exchange multi-pass shell-and-tube apparatus containing tube sheets with heat-exchange tubes fixed in them, placed in a cylindrical case with bottoms and forming end solution chambers with the bottoms of the case, separated by solid partitions adjacent to the walls of the bottoms and tube sheets to the inlet , outlet and pivoting chambers connecting in series to each other the heat transfer pipes of the forward and reverse paths into a single solution path, according to the invention, The respective chambers are equipped with dividing walls installed on the tube sheets between the forward and reverse pipes with the formation of cavities communicating with each other through the bypass openings formed under the bottoms, while the cavities above the solution inlet pipes of each forward and reverse pipes are equipped with honeycomb / mesh bars with direct guides flow stabilization plates mounted to trim the upper edge of the separation walls.

In this case, the dividing partitions are made with a height of at least 4-6d, where d is the inner diameter of the heat exchange tubes. In addition, the honeycomb / cells of the plate grid formed by the plates are made with a side size of not more than 0.6-0.7d. And the plates of the lattice are made of various heights, within 2-3d, and are mounted in the lattice in dimensions of its height, for example, in the following order: longitudinal plates - height 3d, and transverse - 2d.

The technical result of the implementation of the distinguishing features is expressed in the fact that the dividing walls of the forward and reverse tube bundles in combination with honeycombs over the reverse tube bundles significantly increase the degree of uniformity of the spreading of the working flow along the front of the tube grate, which ensures uniform distribution of the flow over almost the entire area of the tube bundles. As a result of the organized flow inlet, almost all heat exchanger tubes participate in the heat exchange, while the effective heat transfer surface is increased and efficient heat transfer in the apparatus as a whole is ensured. In addition, cascading separation of the flow at differently high edges of the plates of the cells of the honeycomb lattice in combination with a certain cell size prevents wall contamination and drawdown of the cells by deposits and have an equalizing effect with minimal loss of hydraulic resistance. The optimal geometric parameters and intervals of the ratios of the sizes of the elements of the apparatus are determined empirically and together provide the expected technical result.

From the analysis of scientific, technical and patent literature of the claimed combination of features, it was not revealed, which allows us to conclude that the claimed technical solution meets the criteria of "novelty" and "inventive step".

An example of a specific implementation of the proposed device is illustrated by drawings, where Fig. 2 schematically shows a solution chamber of a heat-exchange multi-pass shell-and-tube apparatus in a section, Fig. 3 - rotary mortar chamber - view A in Fig. 2. The device comprises a cylindrical casing / housing 1 with tube sheets 2 and 3 placed in it, in which heat transfer tubes of direct 4 and reverse 5, bottoms 6 and 7, with nozzles 8 and 9 for supplying and discharging the working fluid, forming with tube sheets 2 are fixed , 3 end mortar chambers 10, separated by solid baffles 11 into sections-passages, which form the inlet 12, outlet 13 and rotary chambers 14 for serial connection of heat exchange pipes into the solution path. Pipes of direct 4 and reverse 5 strokes in each rotary chamber 14 are separated by partitions 15 made of a height of not more than 4-6 sizes of the inner diameter d of the heat exchange tubes and mounted on tube sheets with the formation of bypass holes 16 under the bottoms 6 and 7. The cavities 17 formed for each rotary chambers 14 above the solution inlet pipes of each forward and reverse stroke are closed at the level of the upper edge of the separation walls 15 with honeycomb grids 18 with straight guide plates 19, 20 for stabilizing the flow. The plates of the honeycomb lattice are made of different heights with sizes from 2 to 3 d and are mounted in the lattice in the following order, for example, longitudinal 19 high 2d, transverse 20 high 3d with the formation of honeycombs 21 with sides ranging in size from 0.6 to 0, 7d.

The device operates as follows.

The processed liquid / solution enters through the pipe into the end inlet mortar chamber of the heat exchanger and sequentially through the heat exchange tubes of the forward and reverse motion of the rotary chambers passes the entire process cycle of heat exchange with the annular coolant and is removed from the apparatus through the outlet chamber and the pipe. Passing through the rotary chambers, the fluid flow from the direct-flow heat exchange pipes enters the cavities bounded by the chamber walls and dividing walls, where it receives a directed flow and uniform velocity distribution over the cross section. Further, bending around the dividing wall through the bypass hole, the fluid flow changes the direction of movement by 180 ° and enters the honeycomb grid, where the vortex flows arising in it are quenched and a directed fluid movement is formed to the tube sheet and to the front of the return heat transfer tubes. Through these pipes, the processed liquid / solution enters the following rotary chambers of a similar design, where the indicated hydrodynamic processes are repeated. From the last tube bundle, the liquid enters the outlet solution chamber and is discharged from the apparatus through the nozzle.

By dividing the pivoting chamber into two cavities with the experimentally achieved optimal ratio of the size of the dividing wall, the bypass hole and the cells of the honeycomb lattice from uneven plates, the conditions are created for preventing the formation of a vortex zone of the transit flows of the treated fluid in front of the front of the return tube bundles, which ensures uniform distribution of the flow across tube bundle pipes. As a result of the flow organized in this way, almost all the heat exchanger tubes participate in the heat exchange, which leads to a rational increase in the heat transfer coefficient of the multi-pass apparatus.

Claims (4)

1. A heat-exchange multi-pass shell-and-tube apparatus containing tube sheets with heat exchange pipes fixed in them, placed in a cylindrical case with bottoms and forming end solution chambers with the bottoms of the case, separated by solid partitions adjacent to the walls of the bottoms and tube sheets, to the inlet, outlet, and rotary chambers connecting sequentially between themselves the heat transfer pipes of the forward and backward paths into a single solution path, characterized in that the rotary chambers are equipped with dividing pipes towns installed on the tube sheets between the forward and reverse pipes with the formation of cavities communicating with each other through the bypass holes formed under the bottoms, while the cavities above the solution inlet pipes of each forward and reverse pipes are equipped with honeycomb / mesh bars with direct flow stabilization guide plates, mounted to trim the upper edge of the partition walls. 2. Heat exchanger multi-pass shell-and-tube apparatus according to claim 1, characterized in that the dividing walls are made with a height of at least 4-6 d, where d is the inner diameter of the heat exchanger tubes. 3. The heat-exchange multi-pass shell-and-tube apparatus according to claim 1, characterized in that the cells / cells of the plate grid formed by the plates are made with a side of a size of not more than 0.6-0.7d. 4. The heat-exchange multi-pass shell-and-tube apparatus according to claim 1, characterized in that the lattice plates are made of different heights within 2-3d and are mounted in the lattice in height dimensions, for example, in the following order: longitudinal plates are 3d high and transverse are 2d high .

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